Gulf of California 2012

Volcanoes and Seamounts

April 17-May 1, 2012

Alarcon Rise is a 50-kilometer-long, asymmetrically spreading mid-ocean ridge segment bounded at the ends by the Pescadero and Tamayo transform faults. The ROV dives on Alarcon Rise will observe and sample the volcanic terrain along the ridge axis, with the primary objective to test the hypothesis that the shallowest central portion of the ridge segment experiences more frequent eruptions and has more vigorous hydrothermal discharge than the deeper portions towards the transform faults that bound the ridge segment.

Using data that will be collected with the mapping AUV on the R/V Zephyr as a separate part of this expedition, we will focus our ROV dives on any newly discovered hydrothermal vent structures and the youngest, least sediment-covered lava flows. We will examine the style of eruptions from ROV observations and samples, and evaluate the frequency of the eruptions by dating samples of the lavas and of fossils in sediments that blanket the flows. A secondary objective on these dives will be to characterize and collect non-vent and vent organisms, should any active hydrothermal vents be discovered.

The Alarcon Seamount ROV dives are planned to make geological observations relevant to understanding caldera formation and explosive eruptions on these near-ridge type of volcanoes. As we have done at the Taney, President Jackson and Vance Seamounts, we will collect samples of lava and pyroclastic deposits from the caldera walls and rims at the Alarcon Seamounts, which rise to 800 meters (2,625 feet) depth.

Research programs at the Monterey Bay Aquarium Research Institute (MBARI) encompass the entire ocean, from the surface waters to the deep seafloor, and from the coastal zone to the open sea. The need to understand the ocean in all its complexity and variability drives MBARI's research and development efforts.